There are things about Tool:
1) In an industry where artists keep releasing albums every year just to be in the limelight and even dead bands want to re-live their old glory by releasing Greatest Hits album, Tool are an exception. They release albums once every 3-5 years.
2) Nothing is as it seems. The motto of the band is "Think for yourself". You will see it reflected in their lyrics and their music.
3) You can keep yourself occupied with finding hidden meanings in their https://lyrics. You can think of drugs, spirituality and angst when you read lyrics and chances are all three themes will fit in.
4) At odd times, you can see an useless track. Actually, combine two songs and lay it on top of another song, you will get a different kind of a song. Yep! Tool can be tricky.
5) They are pranky. They might announce that some book defines all of Tool’s ideologies and urge you to read the book. There may be no such book, but just a play on words. The best example is "Die er Van Satan" from Aenima, which is as if spoken by Satan himself to the crowd. But it is actually a baked eggs recipe in German.
The thing that makes Tool unique is that they can be listened to ad infinitum without thinking about any of those things.
Lateralus
In their whole discography, this is the most spiritualistic album(if you choose to see it that way). Their music can be loosely defined as Progressive metal with elements of Art rock. Actually, I’d say that Genres are "invented" by the record industry to label and push artists. So, the only time you need to worry about classifying Tool’s genre is when you want ease the browsing by Genre in your DAP/PMP/PC.
This is an album I have listened to countless times. My first brush with Tool happened when MTV’s Headbanger’s ball played "Schism". I’ve been hooked since I finally got this album some 5 years after it’s release.
Now, I am not a music reviewer. So, I can only describe the "feel", not how the music is played.
I almost like all the songs in the album. However, if you remove the fillers if you want to and it will sound even better.
My favourite tracks of the album(in no particular order):
Schism - is about the great schism in Christianity. Also apply equally(some say better:) to a lost relationship.
Lateralus - follows Fibonacci sequence. It also(according to Wikipedia) describes the endless desire of humans to know everything.
Parabol/Parabola - Closely resembles the Hindu philosophy of Atman and Maya. But, who knows? It might be about the effects of drugs;-)
Disposition/Reflection - You could listen to these all day. I don’t know why this album always manages to soothe my nerves(Yes! it really has). These tracks could be a good reason for that.
The Grudge - Perhaps a very straight song with not much of hidden meanings. Thinking of it, their album openers have always been good.
Ticks and Leeches - Great drumming and great vocal strain for Maynard James Keenan. Read that they do not play it live as far as possible. You can see why.
The Patient - Another slow song in which the "emo" voice of MJK comes alive.
Update: BTW, the Cover for "Lateralus" happens to be the cover of "Opiate":-)